When I was testing the application, it started to throw errors on the init of the application (the application loads some highly-accessed information from DB to Cache on the init phase):

ORA-12519, TNS:no appropriate service handler found

As I was able to access the database both remotely and locally (through SQL*PLUS), after some research I found that the problem was due to a bug on Oracle DB Express Edition (XE)on how the connections are monitored.

Solution:

Change a system parameter: ALTER SYSTEM SET PROCESSES=150 SCOPE=SPFILE